Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755242AbaGQA73 (ORCPT ); Wed, 16 Jul 2014 20:59:29 -0400 Received: from mail-ig0-f182.google.com ([209.85.213.182]:47125 "EHLO mail-ig0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752706AbaGQA7Z (ORCPT ); Wed, 16 Jul 2014 20:59:25 -0400 Date: Wed, 16 Jul 2014 17:59:22 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Andrea Arcangeli , Vlastimil Babka , Mel Gorman , Rik van Riel , "Kirill A. Shutemov" , Bob Liu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [patch v3] mm, thp: only collapse hugepages to nodes with affinity for zone_reclaim_mode In-Reply-To: Message-ID: References: <53C69C7B.1010709@suse.cz> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 9f1b868a13ac ("mm: thp: khugepaged: add policy for finding target node") improved the previous khugepaged logic which allocated a transparent hugepages from the node of the first page being collapsed. However, it is still possible to collapse pages to remote memory which may suffer from additional access latency. With the current policy, it is possible that 255 pages (with PAGE_SHIFT == 12) will be collapsed remotely if the majority are allocated from that node. When zone_reclaim_mode is enabled, it means the VM should make every attempt to allocate locally to prevent NUMA performance degradation. In this case, we do not want to collapse hugepages to remote nodes that would suffer from increased access latency. Thus, when zone_reclaim_mode is enabled, only allow collapsing to nodes with RECLAIM_DISTANCE or less. There is no functional change for systems that disable zone_reclaim_mode. Signed-off-by: David Rientjes --- v2: only change behavior for zone_reclaim_mode per Dave Hansen v3: optimization based on previous node counts per Vlastimil Babka mm/huge_memory.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2234,6 +2234,30 @@ static void khugepaged_alloc_sleep(void) static int khugepaged_node_load[MAX_NUMNODES]; #ifdef CONFIG_NUMA +static bool khugepaged_scan_abort(int nid) +{ + int i; + + /* + * If zone_reclaim_mode is disabled, then no extra effort is made to + * allocate memory locally. + */ + if (!zone_reclaim_mode) + return false; + + /* If there is a count for this node already, it must be acceptable */ + if (khugepaged_node_load[nid]) + return false; + + for (i = 0; i < MAX_NUMNODES; i++) { + if (!khugepaged_node_load[i]) + continue; + if (node_distance(nid, i) > RECLAIM_DISTANCE) + return true; + } + return false; +} + static int khugepaged_find_target_node(void) { static int last_khugepaged_target_node = NUMA_NO_NODE; @@ -2309,6 +2333,11 @@ static struct page return *hpage; } #else +static bool khugepaged_scan_abort(int nid) +{ + return false; +} + static int khugepaged_find_target_node(void) { return 0; @@ -2545,6 +2574,8 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, * hit record. */ node = page_to_nid(page); + if (khugepaged_scan_abort(node)) + goto out_unmap; khugepaged_node_load[node]++; VM_BUG_ON_PAGE(PageCompound(page), page); if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/